Method for manufacturing aluminum alloy wheel

ABSTRACT

A method is disclosed for production of a single-piece type aluminum alloy wheel. Specifically, the method includes one-piece casting by a casting means to form a disk part and a pre-rim part from a certain aluminum alloy, and spinning the pre-rim part formed from the aluminum alloy by the one-piece casting step to form a rim part of a specified shape. Preferably, the method uses gravity-type casting as the casting method by the casting step. The casting step is carried out such that the disk part is set-established horizontally in a lower part of a mold, such that thereafter the pre-rim part is set-established approximately vertically above and circumferentially centered with respect to the pre-disk part. A plurality of gates-risers are thereafter disposed circumferentially or radially on the pre-rim part. Thus, an overall high strength aluminum alloy wheel is produced with good efficiency.

BACKGROUND OF INVENTION

[0001] 1. Field of the Invention

[0002] The present invention generally relates to a method for production of an aluminum alloy wheel. More particularly, the present invention relates to a method for production of an aluminum alloy wheel by performance of a certain spinning process on a structure (i.e. semi-finished product), formed by gravity-type casting, that forms a single-piece molded wheel having a specified rim shape.

[0003] 2. Background Art

[0004] The structure of a conventional wheel produced from a light alloy (e.g. an automotive aluminum wheel and the like), as shown in FIG. 3, comprises a relatively thickly-shaped disk part 20 and a thinly-shaped rim part 10 that is formed contiguously with the disk part 20. An automotive wheel assembly is built by forming a bead sheet part 110 and 120 on either edge of the rim part 10 for attachment of a tire. However, the cross-sectional width and oblateness of tires, attached to general automotive wheels having this type of structure, have increased in recent years. Thus, the width of the rim part 10, shown in FIG. 3, is also increasing, causing the distance between the disk part 20 and the bead sheet part 110 disposed at one edge of the rim part 10 to increase. During vehicle operation, this results in high loading of the bead sheet part 110 formed at a position displaced from the disk part 20, resulting in concern that cracks and/or other manifestations of stress may occur due to fatigue. Means that have been considered for dealing with this type of problem include thickening of the rim part 10 and the bead sheet part 110. However, such an increase of thickness has many deficiencies with respect to increased mass and the need to ensure interior space.

SUMMARY OF INVENTION

[0005] In one aspect, the present invention relates to a single-piece forming process (method) including first using a casting process for forming a major part of the disk part as a semi-finished product and thereafter using a spinning process for plastic deformation of a part of this semi-finished product used for forming the rim part thereof. The disk part and the rim part are thus formed as a single piece, and the obtained rim is wide.

[0006] The present invention relates to a method for production of a single-piece type aluminum alloy wheel. Specifically, the method includes one-piece casting by a casting means to form a pre-disk part and a pre-rim part from a certain aluminum alloy, and spin-processing by a certain spin-processing means the pre-rim part formed from the aluminum alloy by the one-piece (or single-piece) casting step to form the rim part of a specified shape. Preferably, the present invention uses gravity-type casting as the casting method. Further, casting is carried out such that the pre-disk part is set-established horizontally in a lower part of a mold, such that thereafter the pre-rim part is set-established approximately vertically above and circumferentially centered with respect to the pre-disk part, and a plurality of gates-risers are thereafter disposed circumferentially (or radially) on the pre-rim part.

[0007] According to this type of process, the present invention is capable of efficiently forming (producing) a single-piece type aluminum alloy wheel while controlling distribution of metal grain structure from the disk part to the rim part. In particular, the present invention first pours metal for the part subsequently becoming the disk part, and this part then becomes the part that cools first. Thus the metal grain structure of this part becomes dense, and this results in an increase of strength. Immediately thereafter, the part subsequently becoming the rim part is formed during final melt pouring and cooling. Although conditions of this casting process result in a rough metal grain structure for the final melt pouring, a spinning process is applied to this part to form the rim part so that the distribution of metal grain structure becomes continuous with that of the disk part. Thus, an overall high strength aluminum alloy wheel is formed (produced) with good efficiency by use of this type of spin-forming process.

[0008] Other aspects and advantages of the invention will be apparent from the following description and the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

[0009] FIGS. 1A-1C are a series of explanatory process diagrams showing the overall contents of the present invention.

[0010] FIGS. 2A-2E are a series of explanatory process diagrams showing contents of the spinning-processing step which is the major part of the present invention.

[0011]FIG. 3 is a sectional view of the overall structure of a wheel having a typical wide rim part.

DETAILED DESCRIPTION

[0012] The following description is given in accordance with a preferred embodiment of the present invention and with reference to the accompanying drawings, FIGS. 1A-1C and FIGS. 2A-2E. The preferred embodiment of the present invention relates to a method for production of a single-piece (or one-piece) type aluminum alloy wheel. The basic steps of the preferred embodiment are illustrated in FIGS. 1A-1C. A casting step, illustrated in FIG. 1A, for one-piece forming, includes a casting means that uses a certain aluminum alloy to form a pre-disk part subsequently becoming a disk part 2 and a pre-rim part subsequently becoming a rim part 1. A spinning step, illustrated in FIG. 1B, includes a certain spinning means 5 for forming and processing the aforementioned rim part 1 from a semi-finished product shape, i.e., the aluminum alloy casting formed by casting step, into a rim part 1 that has a certain (or specified) shape. In other words, the embodiment relates to a method for production of an one-piece type aluminum alloy wheel by efficiently forming an one-piece type aluminum alloy wheel, illustrated in FIG. 1C, by combining the casting process, shown in FIG. 1A and the spinning process, shown in FIG. 1B.

[0013] Furthermore, casting comprises a gravity casting method that includes the steps of pouring melt into a cavity, formed by-a mold comprising a plurality of forms 91, 92, and 93, and thereafter cooling. According to the embodiment, a cavity space formed by the lowest part of the gap between the lower form 92 and the upper form 91 is used to produce the part that subsequently becomes the disk part 2. From the perimeter edge part of the cavity, forming disk part 2 in the manner described, a tubular-shaped cavity is provided that extends vertically between the side form 93 and the upper form 91, so as to subsequently form the rim part 1 from the poured melt. A plurality of radially-shaped gates-risers 19 for pouring melt are provided at the upper part of the tubular-shaped cavity forming the rim part 1. The multiple gates-risers 19 connect the aforementioned part forming the rim part 1 to the exterior. These multiple gates-risers 19 can be thought of as being disposed in a ring as viewed from above.

[0014] To utilize a mold having this type of structure, the melt is first poured into the part that subsequently becomes the disk part 2, which becomes the first part to cool down. Thus, the metal grain structure of the disk part 2 becomes dense, being formed by a strong metal grain structure having excellent strength. After performance of the specified casting step in this manner, the mold is then opened, the aluminum alloy casting is removed, and the aforementioned multiple gates-risers 19 are removed by a certain cutting means to obtain the semi-finished product, i.e., the aluminum alloy casting.

[0015] Thereafter, so as to form the rim part 1, shown in FIG. 1B, a certain spinning step processes the tubular part of the semi-finished product casting formed in the manner described above. A special method is adopted for the spinning step of the embodiment. FIGS. 2A-2E are used to explain the spinning step. Firstly, as shown in FIG. 2A, the casting product in the form of the aforementioned semi-finished product, formed by the casting step, is placed on a mandrel-mold 3. Thereafter, the semi-finished product is rotated together with the mandrel-mold 3. Then a roller 5, as a means for spinning, is moved approximately laterally while the roller 3 is pressed to exert a certain pressure against the exterior of the rim surface of the part subsequently becoming the rim part 1. Although the part subsequently becoming the rim part 1 had been formed thickly at the time of casting of the aforementioned semi-finished product, the part subsequently becoming the rim part 1 is stretched during this step, as shown in FIG. 2B and FIG. 2C, to form the rim part 1 having a certain rim width. Moreover, at the start of this type of spinning, a preheat burner (or equivalent device) is used to preheat the mandrel-mold 3 to a temperature of 150° C. to 300° C. The semi-finished product form of the casting product is also subjected to preheating at a temperature of 150° C. to 400° C. in a certain heating furnace (or equivalent device).

[0016] Thereafter, the semi-finished product, having undergone spinning up to nearly the entire width of rim part 1 (FIG. 2C), as shown in FIG. 2D, is subjected to further spinning to form the perimeter of an inner bead sheet part 13. This is done by movement of a roller 5 while the roller 5 applies a certain pressure and moves from the inner bead sheet part 13 to the interior side of a flange part 11. Finally, as shown in FIG. 2E, form-processing of the perimeter of the inner flange part 11 is performed by pressing a roller 55, having a certain cross-sectional shape, against the interior of the flange part 11. During the step of forming the flange part 11, this embodiment utilizes a profiling roller that has a certain shape to match the cross-sectional profile of the flange part 11. The rim part 1, having a certain rim width due to use of this series of spin-form processing (plastic processing), is formed together with the disk part 2 as a single piece. Thus, the distribution of metal grain structure of the rim part 1 is continuous at a coupling part between the disk part 2 and the rim part 1 (i.e., from the outer bead sheet part 12 side to the inner side of the flange part 11). Furthermore, the distribution, itself, of metal grain structure becomes formed in a controlled manner. Thus, according to this embodiment, the rim part 1 has increased strength so that it becomes possible to form the rim part 1 with a wide yet thin profile. Moreover, all parts of the wheel produced in this manner are formed by means for plastic processing. It thus becomes possible to omit material-removal type processing.

[0017] In this embodiment, melt was poured first into the aforementioned disk part 2, and the disk part 2 was the part that first cooled. Thus, the metal grain structure of this part becomes dense, and in turn strength is increased. Immediately thereafter, the part subsequently becoming the rim part is poured and cooled. Although the metal grain structure becomes rough in this cast state, this part is subsequently subjected to processing by the spinning so that the form-processing of this part results in a distribution of metal grain structure that is continuous with that of the disk part. Thus, it becomes possible with high efficiency to produce an aluminum alloy wheel having high overall strength by use of the aforementioned spinning-forming processing means.

[0018] While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims. 

What is claimed is:
 1. A method for production of an aluminum alloy wheel, comprising: one-piece casting to form a disk part and a pre-rim part from an aluminum alloy; and spinning the pre-rim part to form a rim part of a specified shape.
 2. The method of claim 1, wherein the one-piece casting comprises gravity-type casting.
 3. The method of claim 2, wherein the gravity-type casting comprises: set-establishing the disk part horizontally in a lower part of a mold; set-establishing the pre-rim part approximately vertically above and circumferentially centered with respect to the disk part; and disposing a plurality of gates-risers circumferentially on the pre-rim part.
 4. The method of claim 1, further comprising form-processing the rim part together with the disk part to form a single piece, wherein the disk part is coupled to the rim part, and wherein a distribution of metal grain structure between the rim part and the disk part is controlled and continuous.
 5. A single-piece aluminum alloy wheel, comprising: a rim part; and a disk part; wherein the rim part and the disk part are coupled together such that a distribution of metal grain structure between the rim part and the disk part is controlled and continuous.
 6. A single-piece aluminum alloy wheel produced by a process comprising: one-piece casting to form a disk part and a pre-rim part from an aluminum alloy; spinning the pre-rim part to form a rim part of a specified shape; and form-processing the rim part together with the disk part to form a single piece; wherein the disk part is coupled to the rim part, and wherein a distribution of metal grain structure between the rim part and the disk part is controlled and continuous. 